Conventionally, there is disclosed a printer which uses an ink being hardened by an ultraviolet ray irradiation. In the printer, an ultraviolet ray irradiation unit is provided at a rear end thereof such that the ink printed on a target object is hardened. Recently, as for the configuration of the ultraviolet ray irradiation unit, there have been suggested various configurations, each using an LED (light emitting diode) unit as a light source instead of a discharge lamp in view of lowering power consumption and extending life span (see, e.g., patent document 1 and patent document 2).
The LED unit requires to irradiate ultraviolet rays over a wide range in a width direction of the target object, so that an irradiation portion thereof generally has a thin and long line shape. For example, as shown in FIGS. 14A and 14B, there is an LED unit where a plurality of LED modules 101 is installed in one row, each of the LED modules 101 having a lens and an LED chip therein and irradiating ultraviolet rays through the lens. Accordingly, the light is characterized to be irradiated in a line shape. FIG. 14C shows an ultraviolet ray intensity over an irradiation range in a width direction L1 of the LED unit seen from a front portion of the LED unit, and FIG. 14D shows an ultraviolet ray intensity over an irradiation range in a lengthwise direction L2 seen from a side portion of the LED unit.
[Patent Document 1] Japanese Utility Model Registration No. 3151132
[Patent Document 2] Japanese Patent Application Publication No. 2005-203481
The LED unit requires an improvement in the ultraviolet irradiation intensity and uniformity in the irradiation intensity distribution. Moreover, high-density installation using a plurality of LED elements has been attempted. In order to realize the high-density installation, a single LED module has therein a plurality of LED chips. Or, a plurality of LED modules is provided in multiple rows and columns to perform surface emitting.
In order to improve the ultraviolet ray irradiation intensity, there is also disclosed an LED unit in which LED modules 101 as shown in FIG. 14 are arranged in multiple rows (FIGS. 15A and 15B show two rows and three rows arrangement, respectively) such that the irradiation ranges of the LED modules 101 are overlapped with each other, as shown in FIGS. 15A and 15B, for example. However, a fixing member, e.g., a bracket or the like, for adjusting the irradiation directions of the LED modules 101 is required to control the irradiation ranges of the LED modules 101. This leads to an increased number of components and a complicated configuration.
The densely installed LED elements require a heat radiation unit for suppressing a temperature increase, because the heat generation from the LED elements decreases luminous efficiency. For example, each of the configurations shown in FIGS. 14 and 15 includes an air-cooling structure using a heat radiation member made of metal (not shown) or the like. In addition, an LED module employing as a heat radiation unit a water-cooling structure using a coolant is suggested.
However, there has been developed no LED unit with a heat radiation unit capable of improving an ultraviolet ray irradiation intensity and achieving uniform irradiation intensity distribution with a simple configuration.